Well when I found out it was free(if slight limited features), I decided to give it a shot. Been playing it for almost 2 weeks now I think. Not bad, entertaining enough. I mean I spent about a year playing WoW so I'm use to the MMO deal at least some. DCU basically functions like WoW, though my one big grievance is the camera. It can be really annoying with the camera moving on the mouse. But I'm getting pretty use to it now. Other then that I would have to say just how small the game is. While I haven't confirmed it yet, I heard the level cap is 30. My hero right now is 20 so I'm nearly done leveling her up. And then there's the fact that the powers/skills/weapons trees. Not enough points, though I heard you can continue getting skill points even when you hit 30 though no idea how. But I guess if they're planning for the long run it does make some sense since if you got a bunch of points and maxed out powers by lv30 then when they come out with an expansion(aside from the GL one) that increases the level cap then they wouldn't have much else to do with their characters since they got the powers they wanted. But it's kind of a bummer right now, no big though I guess.
Overall it's okay just small considering the only places to really go are Metropolis and Gotham. Though I'm not a 100% on whether the GL expansion gave a new area, I don't think it did. Which seems odd, but oh well.